1. Field of the Invention
The present invention relates to a chemical process for forming metal oxide superconductors of the YBa.sub.2 Cu.sub.3 O.sub.y type (y=6.4-7.1, preferably about 6.9).
2. Description of the Prior Art
As indicated by E. M. Engler in Chemtech, September 1987, pp. 542-551, metal oxide superconductor technology is an extremely fertile area of current research. Perovskite metal oxide superconductors comprising admixtures of metals from Groups IB, IIA and IIIB of the Periodic Table of various types have been identified. A representative class includes those of the formula Y.sub.1 Ba.sub.2 Cu.sub.3 O.sub.y, as well as materials where Y is substituted by Nd, Sm, Eu, Gd, Dy, Ho, Yb, Lu, Y.sub.0.5 -Sc.sub.0.5, Y.sub.0.5 -La.sub.0.5, and Y.sub.0.5 -Lu.sub.0.5, and where Ba is substituted by Sr-Ca, Ba-Sr, and Ba-Ca.
Various processes for forming such superconductor compositions have been proposed. Engler, in the Chemtech article, indicates that such compositions can be formed by mixing and heating oxides or carbonates of the metal precursors (e.g., Y.sub.2 O.sub.3, BaCO.sub.3 and CuO). J. G. Bednorz et al. in Z. Phys. B: Condens. Matter 1986, 64, 189-193 indicated that it is possible to form La-Ba-Cu-O superconductor compositions by a wet chemical procedure using an oxalic acid precipitant. The final oxalate composition gave an impure product which comprised three mixed crystallographic phases as shown by X-ray analysis.